Grinding mill



DBC- 8, 1935- c. P. BRAslNGToN 2,063,363

GRINDING MILL Filed Feb. 4, 1933 3 Sheets-Sheet l 'www WK WLATTORNEYS 'Dec- 8, 1936- c. P. BRAslNGToN 2,063,363

GRINDING MILL Filed Feb. 4, 1933 3 Sheets-Sheet 2 o o /9 Z/ INVENTOR ATTORNEYS Dec. 8, 1936. c. P. BRAslNGToN 2,063,353

GRI'NDING MILL Filed Feb. 4, 1933 3 Sheets-Sheet 5 Patented Dec.` 8, 1936 UNITED s'r-Arlezs PATENT, OFFICE This invention relates to mills of the type exempliiied by pigment grinding mills. The invention likewise relates to a method of controlling the distribution of the substance being ground over the rollers of the mill.

` For the purposes of detail disclosure,-the invention is shown in relation to a three roller pigment grinding mill of the type used in the ink or paint industry. As disclosedthe rollers are of equal diameter, and it may be assumed, for the purposes of this disclosure, thatthe middle roller turns at twice the speedof one of the end rollers and the other end roller at twice the speed of the middle roller. In this way the pigment which is introduced between the first and second roller is drawn downwardly between them onto the surface of the faster moving middle roller and upwardly between the second andthird rollers and off onto the faster moving third or terminal roller.

Adjacent the outer edge of this third roller isI a scraper which removes the pigment from it, the lower end of the scraper or continuation thereof being configurated to constitute a delivery spout.

For ink and paint making, pigment, such as iron blue is mixed with a vehicle such as linseed oil varnish, then the admxture is ground in a mill of the type described for the purpose of reducing the neness of the pigment and for the purpose of wrapping each separate lpigment particle in varnish.

It is conventional to place a relatively large amount of the material to be ground between the first and second rollers so that it may be carried downwardly between them gradually, depending upon the speed of the mill, the thickness of the pigment, the hardness of the pigment, and the pressure under which the rollers are set in relation to each other.

This pool of material between the iirst two rollers naturally tends to overflow the ends of the rollers. On this account it has been conventional in the past to provide end plates (usually of brass) ground to fit the crevice between the two rollers at each end with absolute accuracy and to provide powerful tension means for holding these end plates down hard against the rollers to prevent all possibility of pigmentl getting between the rollers and end plates. While these end plates may be effective for a short period of time, there is always wear and a, great deal of heat generating friction which is not good for the pigment, the rollers, theend plates, or the general efficiency of the mill. In time, moreover, the ink always gets under the end plates and when this takes place the rollers immediately beginv to be ground away. After this once takes place it is almost impossible to reset the end plates or rollersso as to prevent it, so it has been customary in the past just to let nature take its course and when wear becomes too great, to have the rollers reflnished. This refinishing of the rollers is, of course, a very expensive operation. Now, whilel the mill is being used in lthis inefhcient condition, with pigment under the end plates, it

does not grind properly and evenly because the wear at the ends of the rollers reduces their end diameter and the pigment therefore delivered from the ends of the rollers is not as nely ground as the rest of the pigment. It is therefore neces- 15 sary for the workman operating the mill to be very careful to scoop up this less finely ground ink and throw it back again intothe pool in order to maintain the output ofthe mill at uniform quality. If the workman fails so to do and this improperly ground pigment gets through into the finished product, it is more than likely to stop the operation of the lithographie press on which the ink may be used, in which case the company selling the ink is responsible for the loss of time during which the press is being cleaned.

From the foregoing it may be observed that the end plates of roller mills of the type described can'and do cause a great deal of trouble, lessening the eiliciency of the mill, shortening the life of the rollers, and endangering the quality of the product turned out by the mill.

NOW, the idea of this invention, from the method point of view, is not to have end plates in the old sense of the word, but to provide` adjustable constrictions or gates adjacent to the ends of the crevice between the rst two rollers, these constrictions adapted to permit the seepage of the material the mill is grinding toward the ends of the roller, but only at a regulated rate, whereby the second roller carries off the material as rapidly as it seeps toward the roller ends.

From the apparatus point of View, the invention comprises two constrictors shaped very much like end plates, but mounted such a distance away from the rollers that there is no grinding action between the constrictors and the rollers. The distance of sixteen or eighteen one thousandths of an inch is usually sufficient. These constrictors are, however, adjustable for differ- '00 ent pigments or different milling operations. The adjustment disclosed is toward and away from the center of the mill so that for a thin pigment the constrictors can be placed nearer the center, and for a heavy pigment, nearer the roller ends.

Ihe constrictors can therefore be set so that the pigment seeps under them toward the roller ends but is carried off by the second roller at a sufcient rate to avoid any overflow endwise.

By this device the effective grinding length of the rollers is increased over the old type mill by at least the thickness of the two end plates. By this method the rollers do not become worn upon their ends, their life is greatly prolonged, the output of the mill is of absolutely uniform quality, the efficiency of the mill is greater, due to the absence of the friction of the end plates, there is no grinding of the brass of the end plates into the pigment, and the mill requires less adjustment.

Other objects and further advantages will be more fully apparent from a description of the accompanying drawings, in which:

Figure 1 is an end view of a grinding mill looking toward the charging end thereof and showing the present invention incorporated therein.

Figure 2 is an enlarged fragmentary sectional view taken through a constriction plate and its support and through the journal of an adjacent roll of the mill.

Figure 3 is a fragmentary perspective view of the outer side of the plate and its support.

Figure 4 is a side view of the mill.

Figure 5 is an enlarged fragmentary side view of a portion of the mill with the bearings removed for the purpose of illustrating the constriction plate or gate from the outer side.

Figure 6 is a diagrammatic top plan. view of the grinding rolls illustrating the various positions of the plates or gates and showing the line of endwise flow of the substance being ground.

Figures 7A, 7B and '7C are diagrammatic sectional views taken on the lines 1A-1A, 'IE-1B and TC--TC of Figure 5, showing the relation of a particular gate relative tothe rolls and illustrating the seepage of the substance.

Figure 8 is a diagrammatic end View of th rolls further illustrating the flow of substance through the mill.

Figure 9 is a. sectional view taken on line 9 9, Figure 8, illustrating the flow of the substance at theextreme lower end of the gate and substantially at the grinding zone of the rolls.

The mill to which the present invention is shown applied is a three roll mill, although it will be apparent that the invention can be applied to larger mills by making adjustments in the position of the plates.

Referring to the drawings, the grinding rolls are indicated at l and the main support frame at Il. The grinding rolls l0 are journalled in bearings l2, the bearings being of square outer form. The central grinding roll bearing or journal is fixed against movement in the frame whereas the outer journals are slidable in slots |3 disposed longitudinally of the frame for adjustment of the outer rolls toward and from the center roll. The adjustment of these outer rolls is accomplished by means of screw rods I4 and manipulating means l5, the screw rods entering the frame and engaging against the bearings, there being an adjustment device at each corner of the machine.

'I'he details of frame construction and drive are` and a chain of gears I1 which drive all ofthe rolls in the same direction, (see Figure The constriction plates or gates I0 are adjustably supported on an overhead frame I9 consisting of a cross piece 20 and side standards 2| bolted to the top of the side pieces 22 of the frame. This overhead support is disposed directly above the line of contact between the first two rolls at the intake end of the machine. The substance to be ground is initially loaded between these first two rolls and is piled as high as possible as at 23, the quantity depending on the rate of rotation of the rolls and the viscosity of the substance being ground. The quantity introduced therefore necessitatesl end plates for preventing displacement of the substance endwise of the rolls.

For the purpose of adjustment, the constriction plate devices or assemblies are suspended from a screw-threaded rod 24 journalled across and under the overhead support. Its mounting consists of end bearings 25 in the standards 2| and an intermediate bearing 26 bolted to the cross piece. Each gate assembly supported on this rod includes two principal elements, one of .which is the general bracket or body 21 of the device and the other the constriction plate or gate I8 itself, one of these devices being disposed adjacent each side of the machine. l

Each main support element includes a boss 28 at its upper end through which the rod 24 is screw-threaded and a depending arm 29. 'I'he screw-threaded rod has the screw threads at the respective ends reversely formed so that rotation of the rod by means of a crank 30 at an outer end moves the respective devices toward and from each other and along the length of the rolls. The depending arm 29 of each device includes an inner lug 3| which serves as a pivot support for the plate or gate. The gate is attached to `this lug by means of a pivot bracket 32 anda cross pin 33.

The plates are of a width equal to the approximate distance between the centers of the respective rolls and the lower edge of each plate is formed on a curve adapted to be spaced uniformly from the related curvatures of the rolls. Preferably each curved lower edge as related to a particular roll, is formed on a radius fifteen thousandths to thirty thousandths of an inch greater than the radius of the roll, so that when the gate is set to the proper clearance relative to the roll the clearance will be uniform, the center of the radii of the curved surface and the roll coinciding. Generally stated, the radius selected for the curvature of the gate edge in any case can be the mean of the clearance range usable plus the radius of the roll. The pivot bracket connection to the plate is adjustable. For this purpose the bracket includes a vertical portion including a slot 34 traversed by an attaching screw 34's entering the plate or gate through the slot and a vertically disposed set screw 35 loosely extended through a top lug 36 of the pivot bracket and screwed into the upper edge of thel plate. Through this adjustable connection of the pivot bracket to the plate it is possible to vertically adjust the plate by loosening the rear set screw and rotating the top set screw in the appropriate direction, thereby procuring the proper clearance whereby there is no contact between the constriction plate or gate and the rolls.

The pivotal connection of the bracket of the plate to the main element or support arm is for the purpose of permitting inward upward swing of the bracket entirely clear of the rolls when it is necessary'to clean the rolls. Normally and when in position of use each plate or gate depends in a vertical position lies against a set screw 31 adjustably mounted through the lower end of the arm and abutting a boss 38 on the outer side of the plate.

In order to secure the gate or plate in position I swung clear of the roll, a latch or support link 39 is pivotally attached to the plate or pivot bracket 32 thereof and extends outwardly from the plate through a slot 40 in a plate Il secured to the depending arm 29 of the main element 21. Toward the outer end of the latch and in the underside thereof a notch 42 is provided permitting the latch to drop into position when the gate is swung upward whereby the latch 3S engages against the slotted plate and acts as a brace or support for the gate.

The up-swung position of the plateA is shown in Figure 2. Also, it will be noted from'Figure 5 that the gate assembly may be swung laterally by rotation on the screw-threaded adjustment rod. The gates when in position of use are out of contact with the rolls, a clearance of approximately sixteen or eighteen one thdusandths of an inch being maintained depending on the visco/sity of the substance and the weight di rotation of the rolls as well as the spacing of the plates or gates relative to the ends of the rolls.

The amount of seepage under the gates determines the positions thereof and it is most eilicient to place the gatesy as close to the ends of the rolls as possible without permitting escape of the substance endwise of the rolls, thail is, to maintain the substance on the surface of the rolls at all times.

'Iherefore it will be apparent that the gates may either be adjusted longitudinally of the rolls or vertically to obtain the proper position of the gates relative to the'rolls for preventing endwise loss of the substance being ground. If the clearance between the gate and the rolls is. increased it is then necessary to move the gates in from the ends of the rolls because of the increase in seepage under the gates. On the other` hand if the gates are vertically adjusted to move them closer to the rolls, then they may be placed near the ends of the rolls because the seepage is less.

Since there is no contact between the gates and the rolls there is no friction, thus eliminating wear and preventing heating of the roll. Prevention of undue wear at this point maintains the smooth surface for the rolls and insures good grinding results from one end of the roll to the other. Heating of the roll would cause discoloration of pigment especially in case of paint grinding, so that prevention of heat prevents damage to the substance being ground. Moreover, where there is no contact between the gate and rolls, the eiliciency of the machine is greater since there is no power loss such as would occur in the old type of mill where the plates were acting as brakes on the roll surfaces.

For the purpose of describing in detail the control or regulation of the substance being ground by means of the adjustable gates, the diagrammatic views, Figures 6 to 9 inclusive, are hereinafter referred to. In those instances where a relatively viscous substance is being ground, the gates may be set close to the ends of the rolls inasmuch as the seepage under the roll and through the clearance takes place slowly, the views illustrating the slow spread of a thick material.

It is desirable to set the gates as close to the ends of the rolls as possible for` the reason that# the grinding rolls then operate in maximum emciency, all available length of the roll being used. Therefore, as illustrated the rate of ow of the substance having been determined it is desirable to `have it substantially spread out over the entire length of the last or discharge roll.

Figure 6 illustrates both an extreme outer position for the gates and' an extreme inner position, the latter being in the case where the substance is extremely thin or liquid. It has been determined that by virtue of they clearance under the gate which may range from fifteen .thousandths to thirty thousandths of an inch clearance the substance seeping under the gate does not engage the under edge of the plate but iiows closely along the rolls. `It will be noted that the substance seeping underv the plates is being ground at all times. Thus by either vertical `or longitudinal adjustment of the gates depending on the-viscosity of the substance the rate of ilow or seepage under the gates may be regu-A lated and maximum grindingy eiiiciency of the machine obtained.

Having described my invention, I desire to' be limited only by the ensuing claimsi 1. In a grinding mill, grinding rolls, gates mounted between and at the ends of the rolls for obstructing undue endwise movement of the substance being ground, the surfaces of said gates adjacent to the rolls having curvatures concentric to those of the rolls but on slightly greater radii, supports sustaining the gates in positions slightly clear of contact with the rolls, adjustment devices for adjusting the gates longitudinally of the rolls and adjustment devices for adjusting the gates toward and from the roll surfaces.

2. In a grinding mill, grinding rolls," platesy suspended between and at the ends of the rolls obstructing undue endwise movement, supports mounting said plates in positions providing a unif form gap relative to the rolls whereby a certain amount of the substance being ground may spread toward the ends of the rolls and an ad`- justment device for moving the plates simultaneously longitudinally of the rolls toward and from each other.

3. In a grinding mill, a series of grinding rolls, an end gate at each end of adjacent rolls and depending into `the space between the rolls, an overhead support including a rotatable screw shaft having reversely formed threads on the respective ends thereof, means for rotating said screw, supporting arms suspended from the screw rod and in screw-threaded engagement therewith, pivot brackets on said gates pivotally connected to said depending arms, and screw means between said gates and said brackets for vertical adjustment of the gates.

4. In a grinding mill, a series of grinding rolls, an end gate at each end of adjacent rolls and depending into the space between the rolls, an overhead support including a rotatable screw shaft having reversely formed threads on the respective ends thereof, means for rotating said screw, supporting arms suspended from the screw rod and in screw-threaded engagement therewith, pivot brackets on said gates pivotally connected to said depending arms, screw means between said gates and said brackets for vertical adjustments of the gates, latches between the gates and arms whereby the gates may be swung upwardly and supported in up-swung position, and adjustable stops on` the'arms engaged by the gates when Iin position of use for maintaining the gates in vertical positions against outward working pressure induced by the substance piled between the rolls. y

A 5.`\In a grinding mill. a pair of grinding rolls, plates `at the ends of the rolls depending into the space between the rolls and preventing undue endwise movement of the substance piled between the rolls, means for pivotally supporting said plates, latches between the plates and sup' ports adapted to secure the plates when swung upwardly and away from'the rolls, and stops for preventing endwise movement of the plates under the pressure'induced by the substance piled between the rolls.

' 6. In a grinding mill, grinding rolls differentially speeded,y end gates adjustably supported toward the ends of the rolls, said gates adjustable l longitudinally of and' uniformly spaced as'much as about thirty one-thousandths of an inch from the surface of the rolls, whereby endwise flow oi"k the substance loaded' between the rolls is restricted and a certain amount of flow beneath the gates and along the rolls is permitted and regulated. I

7. In the art of grinding viscous substances, the method of controlling the substance passing through a roll mill having grinding rolls differentially speeded, comprising, partially obstructing the endwise ow of a pool of the substance troughed between the intake rolls of the mill but permitting a regulated uniform spread of the substance toward the ends of the rolls` and conveying the substance which is spreading endwise from the obstructions through the rolls before the spreading substance reaches the ends of the rolls by corelating the amount of regulated spread of the substance with the differential of the roll speeds,` the regulated spread being of suilicient thickness for a grinding action of the same degree as the grinding action taking place between the Vobstructions whereby the maximum available grinding length of the rollsv is utilized. 8. In a grinding mill, a pair of grinding rolls, plates at the ends of the rolls, said plates depending into the space between the rolls and slightly spaced therefrom and preventing undue endwise movement of the substance to be ground piled between the rolls, means for pivotally supporting said plates andpermitting the plates to be swung longitudinally of the rolls and upwardly therefrom, andf stops for preventing endwise movement of the plates under the pressure induced by the substance piled between the rolls.

9,'In a grinding mill, grinding rolls, plates suspended between and at the ends of the rolls for obstructing undue endwise displacement of a pool of substance between the plates, means for ,y aoeasea supporting said plates clear of contact with the rolls, the surfaces of the plates adjacent to the rolls being formed on curvatures taken on radii concentric to those of the rolls whereby a certain amount of substance is free to flowunder the' plates without contacting the same. i

10. In a grinding mill, grinding rolls, plates suspended between and at the ends of the rolls for obstructing undue endwise displacement of a pool of substance between the plates, means for supporting said plates clear of contact with the rolls, the surfaces of the plates adjacent to the rolls being formed on curvatures taken on radi! concentric to those of the rolls whereby a regulated amount of substance is free to flow under the plates without contacting the same, and an adjustment device for moving said plates simultaneously and in equal amounts toward or from the respective ends of the roller.

11. In a` grinding mill, grinding rolls, plates suspended between and at the ends of the rolls for obstructing undue endwlse displacement of a pool of substance between the plates, means for supporting said plates clear of contact with the rolls, the surfaces of the plates adjacent to the rolls being formed on curvatures taken on radii substantially concentric to those of the rolls and at least as far away from the rolls at the nip region of the rolls as they are distant from the rolls at their outer ends whereby a certain amount of substance is free to ow under the plates without contacting the same.

12. In a, grinding mill,'a pair of grinding rolls,

plates disposed toward the ends of the rolls, said plates depending into the space between the rolls for obstructing undue endwise displacement of a pool of substance between the plates, means for supportingy said plates clear of contact with the rolls, the space between the plates and the rolls being greater than the thickness'of the nlm of substance flowing under the plates and therefore providing an air gap between the substance and the adjacent 'surfaces of the plates.

13'. 'I'he method of controlling the feed of a substance being lground in a roll mill, consisting 

